WX temp charts showing some movement. From the familiar pattern in week 1 (All Europe except Scandinavia above norm, freezing weather north of a line from the Baltic to the S Urals) there is a breakout with freezing weather spreading SW-wards to affect Germany and the Alps. Britain and France are also colder while there is a compensating bulge in milder weather to the N of Ukraine. Pptn (some of which will be snow) in week 1 for Britain, France and across to the Baltic States; in week 2 this splits into three, Norwegian coast, Biscay and S Russia, Britain at least in the S fairly dry.

GFS Op - Current zonal W-lies with HP over N France collapsing by Wed 7th with LP from mid-Atlantic approaching to link up with a deeper area already over S Sweden. becoming a defined centre in its own right Fri 9th 975mb Cornwall with trough lying along the Channel, and E-lies for most of Britain. (Other charts suggest heavy snow across the Midlands but the far S missing out). This LP gets sucked into the general circulation in Sweden leaving weak N-lies behind. By Wed 14th HP 1035 mb Ireland dominates Britain but fails to establish and by Sun 18th there's yet another Scandinavian LP 980mb Norway with Britain under NW-lies, looking rather cold in the NE.

ECM - a critical difference Fri 9th in that the LP and trough lie across N England/S Scotland so snow more likely further N. However it then dives S-wards 965mb Brittany Sat 10th so the S coast does get a shot of cold weather, especially as the following N-lies are stronger - but just as brief as in GFS. 

GEFS - In the S, temps decreasing by fits and starts to the norm by Sat 10th, then a cooler period of 4 or 5 days (op & control much colder than the pack at this time) but mean back to norm by Sun 18th, usual scatter on either side. Heavy rain either side of Fri 9th, some chances of snow on the tail end of this from the Midlands N-wards. In Scotland, temps down, up and down again when the cold period starts, but here earlier on Wed 7th before back to norm as for the S. Rain in two batches 7th and 9th, and as the cold period is definitely colder, quite a good chance of snow on the 9th. NE England more like Scotland, NW England more like the S.

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I dont think this is getting resolved anytime soon; tiny differences in LP development lead to massuve differences regarding snow potential.

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Can't really complain this morning.  A cold spell looks like starting in a weeks time. How cold and snowy who knows, but it looks snowier  than the January spell. Famous lasts words maybe.

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https://www.theweatheroutlook.com/charts/gefs/gefsenswind_10mb60.png?w=800&colors=128 

Hi this is my first post.  Does this graph indicate a possible SSW?  Thank you.

https://www.theweatheroutlook.com/charts/gefs/gefsenswind_10mb60.png?w=800&colors=128 

Hi this is my first post.  Does this graph indicate a possible SSW?  Thank you.

Hi, welcome to TWO!

You're right - the graph has a few members showing a major SSW (reversal), including the operational run. Possible, but unlikely is how I'd sum that up.

The ECM ensembles show a similar picture:

https://charts.ecmwf.int/products/extended-zonal-mean-zonal-wind?area=nh&base_time=202402010000 

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https://www.theweatheroutlook.com/charts/gefs/gefsenswind_10mb60.png?w=800&colors=128 

Hi this is my first post.  Does this graph indicate a possible SSW?  Thank you.

Welcome! I think it indicates that another SSW is possible, although I would not say “probable” at this stage.

Edit: Darren beat me to it!

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GEM is the sort of evolution I’m looking for 😂😂

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A bit more confident this morning. Normally it's a case of let's get the cold in first....however last few spells and in previous years, its a case of let's get the PPN in as well.
 

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Hi, welcome to TWO!

You're right - the graph has a few members showing a major SSW (reversal), including the operational run. Possible, but unlikely is how I'd sum that up.

The ECM ensembles show a similar picture:

https://charts.ecmwf.int/products/extended-zonal-mean-zonal-wind?area=nh&base_time=202402010000 

I can't remember a winter where the Strat has taken such a battering. We've had a couple of nr misses and a SSW already. Seems unusual. 

 

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I can't remember a winter where the Strat has taken such a battering. We've had a couple of nr misses and a SSW already. Seems unusual. 

 

I agree. The addendum is that despite the battering it has taken and some of the other background signals being favourable, this winter remains snowless in most of the UK.

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I agree. The addendum is that despite the battering it has taken and some of the other background signals being favourable, this winter remains snowless in most of the UK.

just been saving itself up for February !

Here's a snapshot of the GEFS 850hPa temp tracker for London. (Full version here https://www.theweatheroutlook.com/tracker/tmp850  with login)

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Here's the GFS 00Z snow depth chart for 11/02. I've long suspected the value it uses for snow density has a tendency to be too low for the UK. Therefore, I'm going to add a version (hopefully in the next couple of days) of this chart which uses a higher value to see how it performs in comparison. 

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I agree. The addendum is that despite the battering it has taken and some of the other background signals being favourable, this winter remains snowless in most of the UK.

I cant even remember seeing back edge snow any more in more than 20 years, as a front cleared.

It was oh so common in the 80s
 

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I'd remind people to not yet get too excited by this. One very likely scenartio, hinted by the ECM is the low overdevelops before it gets to the UK. If it occludes then mild air will mix in north of the triple point and the airmass gradients across the fronts will reduce. If that happens snow will be restricted to northern scotland and probably only high ground. The GFS scenario or the GEM scenario which develop the low less are also plausible but so is the low being less developed which will essentially mean no snow at all and a northerly toppler. Uncertainty is very high, much higher than for the last cold spell which didn't deliver for most.

On the plus side, we do come reasonably close to the reliable timeframe by the 12Z set today. High res models should get this fully in range by tommorow.

EDIT: I should add that the overdevelopment scenario is much more common on the ensembles than it should be given the OPs; yesterday the OP was an outliar so the high res models do seem to be picking up on some tiny detail that limits development. I do worry though that we could very easily revert to the overdevelopment scenario which was overwhelmingly favoured on the GEFS yesterday.

 

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I cant even remember seeing back edge snow any more in more than 20 years, as a front cleared.

It was oh so common in the 80s
 

It inutitively makes sense though. In order to get backend snow you need cold air to advect in very very strongly and when that happens it dries out and weakens the precipitation.

A far easier way to get snow is for the cold front to start stalling and develop a wave (secondary low) on it and 'turn into a warm front' so to speak. That scenario produces snow quite efficiently.
 

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It inutitively makes sense though. In order to get backend snow you need cold air to advect in very very strongly and when that happens it dries out and weakens the precipitation.
 

In today's climate, yes. In the old days - not so much, you didn't need a such a depth of anomalous cold to do it. You're too young to have seen the early to mid 80s, and believe you me - you really missed out!

I'm sure the same could be said of us 80s kids by those who were around in the 60s, mind you. 😂

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I think what's going on here is that in principle we have a zonal pattern albeit a somewhat weak, unusual one with a deep high over the arctic and the tropospheric PV located over scandanavia rather than Canada. Alone this causes a northerly toppler at most, but the other factor is a scrap of PV that breaks away from the main vortex over the Newfoundland area and sluggishly moves eastward. The main jet stream is to the north of this cold core feature so the surface low struggles to intensify.

But this scrap of tropospheric PV rejoins with the main polar vortex as the surface LP hits the UK which makes conditions favourable for intensification as the surface low ends up near the jetstream. Its how early or late this merger occurs that seems to impact conditions, but its also a bit more than that. GEM illustrates a scenario where the LP doesn't really develop at all after the merger because the LP asociated with the main polar vortex develops instead since the surface LP is closer to the jet.

Its very complicated, and somewhat reminiscant of many Northeasters in the US where two cold core troughs, one from the midwest and one from the carribean merge causing wildly dirvergent snow forecasts as models struggle to handle this merging process and how the surface LP is affected by it.
 

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I agree. The addendum is that despite the battering it has taken and some of the other background signals being favourable, this winter remains snowless in most of the UK.

I think a lot of the reason for that has been the presence of HP to the south of the UK for a lot of the winter thus far. It was said by one or two people here before Christmas that those heights to the south, as we are seeing at the moment and for much of the time during December, would likely be the biggest obstacle to getting widespread cold and snowfalls and so it has proved.

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I think a lot of the reason for that has been the presence of HP to the south of the UK for a lot of the winter thus far. It was said by one or two people here before Christmas that those heights to the south, as we are seeing at the moment and for much of the time during December, would likely be the biggest obstacle to getting widespread cold and snowfalls and so it has proved.

I said that. I also provided evidence which shows that pressure anomalies to the south of the UK have increased in recent decades. 

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